1. Field of the Invention
The present invention relates to a method of manufacturing an electrophotographic photosensitive member and a jig used therein. More specifically, the present invention relates to a method of manufacturing an electrophotographic photosensitive member, which has a non-monocrystalline deposited film comprising silicon atoms and hydrogen atoms formed on an aluminum substrate containing silicon atoms according to a plasma CVD method; the present invention also relates to a jig used in such method.
2. Related Background Art
As the substrate for formation of layer or layers to be deposited on an electrophotographic photosensitive member, glass, heat-resistant synthetic resin, stainless steel, and aluminum have been proposed. Metals have often been used from a practical point of view, however, because the substrate must be compatible with an electrophotographic process such as charging, exposure, development, transfer and cleaning and also because the exact position of the surface of the electrophotographic photosensitive member must always be maintained inside the main body of the apparatus with high accuracy in order to keep the image quality. Among many kinds of metal, aluminum is one of the most suitable materials for the substrate of electrophotographic photosensitive member due to good processing property, low cost and light weight.
Technology concerning quality of material for the substrate of electrophotographic photosensitive members is described in U.S. Pat. No. 4,702,981 and Japanese Patent Application Laid-Open No.60-262936. U.S. Pat. No. 4,702,981 discloses a technology to a obtain good image quality amorphous silicon electrophotographic photosensitive member by forming the support of aluminum alloy containing less than 2,000 ppm of Fe. Furthermore, U.S. Pat. No. 4,702,981 also discloses the procedures in which a cylindrical substrate is cut by a lathe and mirror finished and then amorphous silicon is formed by glow discharge. Japanese Patent Application Laid-Open No. 60-262936 discloses an extruded aluminum alloy that is superior in vapor deposition of amorphous silicon, which contains aluminum as major component, 3.0-6.0 wt % of Mg and small amounts of impurities such as less than 0.3 wt % of Mn, 0.01 wt % of Cr, 0.15 wt % of Fe and 0.12 wt % of Si. Cleaning of the substrate, however, is not described in the above-described patent literature.
Technology concerning a method for processing the substrate of electrophotographic photosensitive member is described in Japanese Patent Application Laid-Open No.61-171798, which discloses a technology to obtain an electrophotographic photosensitive member such as high quality amorphous silicon by cutting the substrate with a cutting oil of specific composition. It is also disclosed there that the substrate is cleaned with triethane (trichloroethane: C2H3Cl3) after cutting.
Technologies concerning surface treatment for substrates of electrophotographic photosensitive member have been proposed in Japanese Patent Application Laid-Open Nos.58-014841, 61-273551, 63-264764 and 1-130159.
Japanese Patent Application Laid-Open No.58-014841 discloses a technology for obtaining uniform oxide film by removing a natural oxide film on a surface of an aluminum support and immersing it into water at a temperature of 60xc2x0 C. or higher.
Japanese Patent Application Laid-Open No.61-273551 discloses a technology of cleaning as pretreatment of substrate such as alkali cleaning, trichloroethylene cleaning and UV irradiation cleaning by mercury lamp when electrophotographic photosensitive member is produced by vapor depositing Se or the like on an aluminum substrate. It is also disclosed there that liquid degreaser cleaning, vapor degreaser cleaning and pure water cleaning should be done to remove oil and fat attached on surface of cylindrical aluminum substrate as pretreatment for UV irradiation cleaning.
Japanese Patent Application Laid-Open No.63-264764 discloses a technology of making substrate surface roughened by water jet.
Japanese Patent Application Laid-Open No.1-130159 discloses a technology of cleaning a support of a electrophotographic photosensitive member by water jet. It cites Se, organic photoconductive member and amorphous silicon as examples of photosensitive member. It does not discuss at all, however, the possible problems between film formed by plasma CVD method and cleaning by water jet.
On the other hand, there is a known technology, as disclosed in Japanese Patent Application Laid-Open No.60-876, of injecting carbonic acid gas into super pure water to prevent discharge breakdown due to static electricity on wafer surface. However, this technology is a countermeasure for static electricity generating on highly resistive substrate like wafer and nothing is discussed there on the measures for conductive substrates like aluminum.
Various kinds of materials including inorganic materials like selenium, cadmium sulfide, zinc oxide, and amorphous silicon and organic materials like phthalocyanine have been proposed as composition materials for photosensitive members including photoconductive film used for electrophotographic photosensitive members. Among them, non-monocrystalline deposited films containing silicon atom as a major component, such as amorphous silicon, and amorphous silicon that contains hydrogen and/or halogen (such as fluorine and chlorine) for compensation of dangling bonds, have been proposed as photosensitive members of high performance, high durability and free of contamination. Some of them have been used in practice. One example is U.S. Pat. No. 4,265,991 disclosing technology for an electrophotographic photosensitive member whose photoconductive layer is formed mainly of amorphous silicon.
As methods for forming these non-monocrystalline deposited films that contain silicon atom as major component, many conventional methods are known such as a sputtering method, a thermal starting gas decomposing method (thermal CVD method), an optical starting gas decomposing method (optical CVD method), and a plasma starting gas decomposing method (plasma CVD method).
Plasma CVD method, which is a method for decomposing the starting gas by direct current, high frequency wave (including RF wave and VHF wave) or microwave glow discharge to form thin deposited film on the substrate is most suitable for formation of amorphous silicon deposited film for electrophotograph and has been more widely used. In particular, microwave plasma CVD method, which is a plasma CVD method using microwave glow discharge decomposition as method of forming deposited film, has recently been noted from the industrial point of view.
Microwave plasma CVD method has advantage of high decomposition rate and high efficiency in use of the starting gas over other methods. One example of micro wave plasma CVD method making best use of such advantage is described in U.S. Pat. No. 4,504,518, which intends to obtain high quality deposited film at a high deposition rate by microwave plasma CVD method at a low pressure of not higher than 0.1 Torr.
Technology for further improving the efficiency of use of the starting gas by microwave plasma CVD method is disclosed in Japanese Patent Application Laid-Open No.60-186849. Briefly, this technology is to locate the substrates so as to surround the inlet means of microwave energy and form an internal chamber (discharge space) so that the efficiency of use of the starting gas may increase significantly.
Japanese Patent Application Laid-Open No.61-283116 discloses improved microwave technology for production of semiconductor component. Namely, the technology is to improve the characteristics of deposited film by placing electrode (bias electrode) in the discharge space for control of plasma potential and applying the desired voltage (bias voltage) to the bias electrode for controlling ion impact on the deposited film.
In the case aluminum alloy cylinder is used as the substrate, a typical production method of electrophotographic photosensitive member according to these conventional technologies is executed as follows.
A diamond cutting tool (trade name: MIRACLE BITE manufactured by Tokyo Diamond K.K) is set on lathe with air damper for precision cutting (manufactured by PNEUMO PRECISION INC.) in such a manner that the tool is kept to have a relief angle of 5xc2x0 against the center line of the cylinder. Then the substrate is vacuum-chucked to the rotary flange of the lathe and mirror-finished to obtain 108 mm outside diameter under condition of 1,000 m/min. peripheral speed and 0.01 mm/R delivery speed while jetting kerosene through attached nozzle and at the same time sucking chip through attached vacuum nozzles.
Then, this substrate cut is cleaned with trichloroethane to remove cutting oil and chip remaining on surface.
Next amorphous silicon based deposited film is formed on these mirror finished and cleaned substrates by an apparatus shown in FIG. 1, for forming deposited film of photoconductive component based on glow discharge decomposition method.
FIG. 1 is a schematic transverse sectional view of one example of typical plasma-activated CVD apparatus. In this figure, reference numeral 601 denotes the whole reaction vessel, reference numeral 602 denotes a cathode concurrently functioning as the side wall of reaction vessel, reference numeral 603 denotes a gate which becomes the upper wall of the reaction vessel and reference numeral 604 denotes the bottom wall of the reaction vessel. The cathode 602 described above is insulated respectively with upper wall 603 and bottom wall 604 by insulator 605.
Reference numeral 606 denotes a substrate placed in the reaction vessel installed in a metal substrate holder 607, and the substrate 606 is connected to ground to become anode. Inside the substrate 606, a heater 608 for substrate is installed to heat the substrate to a predetermined temperature before the film formation, to maintain the substrate at a predetermined temperature during the film formation and to give annealing treatment to substrate after the film formation. Reference numeral 609 denotes an inlet pipe for starting material gases for formation of deposited film, and the starting material gases inlet pipe 609 has many gas releasing holes 610 for releasing starting material gas into the reaction space. The other end of the starting material gas inlet pipe 609 is connected to a starting material gas supply system 612 for formation of deposited film through a valve 611. Reference numeral 613 denotes an exhaust pipe to exhaust the inside of the reaction vessel, and the exhaust pipe 613 is connected to an exhausting device 615 such as a vacuum pump through an exhaust valve 614. Reference numeral 616 denotes a means for applying voltage to an cathode 602.
Procedure for operating such deposited film formation apparatus by plasma CVD method is as follows. That is, gases in the reaction vessel is exhausted by vacuum through the exhaust pipe 613, and simultaneously the substrate 606 is heated to a given level of temperature and is maintained at a predetermined temperature by the heater 608. Then, in the case of forming a-SiH deposited film formation, the starting material gas such as silane, is introduced into the reaction vessel through the starting material gas inlet pipe 609. Thus starting material gas is fed to the reaction vessel through the starting material gas releasing holes 610 of the starting material gas inlet pipe 609. At the same time, while doing above operation, plasma discharge is generated by applying, for example, high frequency between the cathode 602 and substrate (anode) 606 from voltage applying means 616. Thus starting material gas within the reaction vessel is excited to form radical particles of Si*, SiH*, etc. ([*] denotes excited state), electrons, ion particles, etc. Chemical interaction between these particles or between these particles and the substrate surface forms deposited film on the subs ate surface.
In the case of forming the electrophotographic photosensitive member comprising a-Si, for example, the substrate holder is inserted into the inside of cylindrical substrate because it is necessary to transport the cylindrical substrate into the reaction vessel and hold it there. This practice of inserting the substrate holder into the inside of the cylindrical substrate is generally done also because it is needed to have auxiliary substrates over and under the substrate for the purpose of making the characteristics uniform as disclosed in, for example, Japanese Patent Application Laid-Open No.60-86276.
However, these conventional methods of manufacturing electrophotographic photosensitive member leave several problems unsolved yet, in order that they may satisfy the need for more uniform film quality and much higher optical and electrical properties and also for steady, stable and highly efficient (high yield) production of deposited film making better image quality in image formation by electrophotographic process.
In other words, higher image quality, higher speed and higher durability are required for electrophotographic apparatus at present. Accordingly, further improvement for longer durability under every probable environment as well as optical properties, electric properties and uniformity is requested for electrophotographic photosensitive members while maintaining higher chargeability and higher sensitivity. In particular, much further improvement of the image properties for electrophotographic photosensitive members is now requested since optical exposure system, development apparatus, and transfer apparatus inside electrophotographic apparatus have been improved for better image properties.
Under such circumstances, locational irregularity of characteristics in an electrophotographic photosensitive member could become a big problem in a high speed continuous image forming system such as a high speed copying system, facsimile system, and printer system using a digital system of coherent light source, in particular, like laser, although it has not necessarily been a problem, or could be neglected in some cases for copying system with conventionally required extent of speed and resolution. In particular, for color copying machines that have become recently popularized, it could be a serious problem because difference in the reproduced color and uneven color are clearly and visually identified.
Furthermore, recent improvement in the resolution of image has now required the reduction of image defects in white and black dots, so-called xe2x80x9cspotxe2x80x9d; now reduction in much smaller size spot in particular is required which has not been a problem conventionally. Most causes for such spot are abnormal growth of the film called spherical projection; decrease of its number is extremely important.
Conventional application of copying machine has been mainly for so-called xe2x80x9cline copyxe2x80x9d in which the manuscript comprises letters only. As the image quality of copying machine has been improved in recent years, documents to be copied tend to include halftone such as photos; and these problems such as spot and unevenness or nonuniformity resulting from locational irregularity of characteristics have become serious and their solutions become necessary.
It is required, therefore, that improvement in layer structure, chemical composition of each layer and production method should be made from overall point of view so that problems described above may be solved while the characteristics of electrophotographic photosensitive member itself should be improved.
An object of the present invention is to provide a method of manufacturing an electrophotographic photosensitive member inexpensively, stably, and at a high yield where a high speed forming is realized with easy handling and to provide a jig for this method, by overcoming abovementioned various problems associated with conventional manufacturing methods for electrophotographic photosensitive members.
Another object of the present invention is to provide a method of manufacturing electrophotographic photosensitive members which can result uniform and high quality image and to provide a jig for this method, by overcoming generation of image defect problem which is especially remarkable in plasma CVD method.
A further another object of the present invention is to provide a method for manufacturing an electrophotographic photosensitive member in which an aluminum substrate is fitted on a substrate holder and a functional film comprising a non-monocrystalline material containing silicon atoms as the matrix is formed by low pressure chemical vapor deposition on the surface of the substrate, which comprises before the step of forming the functional film the step of cleaning the surface of the substrate with water in which carbon dioxide is dissolved, wherein the substrate holder comprises a metal as the matrix and has formed ceramics at least on the inner surface.
A further another object of the present invention is to provide a jig used in a method for preparing a functional film by low pressure chemical vapor deposition on an aluminum substrate fitted on the jig comprising a metal as the matrix and having ceramics formed at least on the surface opposite to the surface on which the aluminum substrate is fitted.